The present invention, in some embodiments thereof, relates to method and system of imaging and, more particularly, but not exclusively, to method and system of medical imaging.
Volumetric scans such as CAT scans, PET scans, CT scans, MRI scans, Ultrasound scans, Laser 3D scanners, and the like are commonly used, particularly in the medical industry, to observe objects within a structure that would otherwise be unobservable. These scans have greatly advanced the capability of professionals such as doctors. Conventional volumetric scan is intended to produce a volumetric image of a large volume of the body at high resolution. The ability to perform a volumetric scan with high resolution requires a large number of detectors, a fine motion control, and abundant processing resources for allowing the acquisition of a high resolution volumetric image in a reasonable time. Furthermore, as the volumetric scan images a relatively large area, such as the torso, the patient radiation dose is relatively high, for example when the volumetric scan is a CT scan.
Usually, volumetric imaging of a body structure is a multi-stage process. First biochemical, radioactive and/or contrast agents may be administered. Then, measurements are taken at a set of predetermined views at predetermined locations, orientations, and durations. Then, the data is analyzed to reconstruct a volumetric image of the body structure and an image of the body structure is formed. The imaging process is sequential, and there is no assessment of the quality of the reconstructed image until after the measurement process is completed. Where a poor quality image is obtained, the measurements must be repeated, resulting in inconvenience to the patient and inefficiency in the imaging process.
The volumetric scan is usually performed by orbiting detectors from multiple directions in order to provide sufficient information to reconstruct a three-dimensional image of the radiation source by means of computed tomography. The detectors are typically mounted on a gantry to provide structural support and to orbit the detector around the object of interest. If the detector is a nuclear medicine detector, such as scintillation detector or CZT detectors, for example Single photon emission computed tomography single photon emission computed tomography (SPECT) and positron emission tomography (PET) systems detector, a collimator that is used to restrict radiation acceptance, or the direction of ray travel, is placed between it and the object being imaged. Typically this collimator is constructed to provide a multiplicity of small holes in a dense, high-atomic-number material such as lead or Tungsten. The rays will pass through the holes if they travel in a direction aligned with the hole but will tend to be absorbed by the collimator material if they travel in a direction not aligned with the holes.
During the last years, a number of non-orbiting tomographic imaging systems have been developed. For example U.S. Pat. No. 6,242,743, filed on Aug. 11, 1998 describes tomographic imaging system which images ionizing radiation such as gamma rays or x rays and which: 1) can produce tomographic images without requiring an orbiting motion of the detector(s) or collimator(s) around the object of interest, 2) produces smaller tomographic systems with enhanced system mobility, and 3) is capable of observing the object of interest from sufficiently many directions to allow multiple time-sequenced tomographic images to be produced. The system consists of a plurality of detector modules which are distributed about or around the object of interest and which fully or partially encircle it. The detector modules are positioned close to the object of interest thereby improving spatial resolution and image quality. The plurality of detectors view a portion of the patient or object of interest simultaneously from a plurality of positions. These attributes are achieved by configuring small modular radiation detector with collimators in a combination of application-specific acquisition geometries and non-orbital detector module motion sequences composed of tilting, swiveling and translating motions, and combinations of such motions. Various kinds of module geometry and module or collimator motion sequences are possible, and several combinations of such geometry and motion are shown. The geometric configurations may be fixed or variable during the acquisition or between acquisition intervals. Clinical applications of various embodiments of the tomography invention include imaging of the human heart, breast, brain or limbs, or small animals. Methods of using the non-orbiting tomographic imaging system are also included.
Another example is described in United States Patent Application 2010/0001200, published on Jul. 1, 2010, which describes an imaging system for radioimaging a region of interest (ROI) of a subject. The system includes a housing, a support structure, which is movably coupled to the housing, and at least one motor assembly, coupled to the housing and the support structure, and configured to move the support structure with respect to the housing. The system also includes at least two detector assemblies, fixed to the support structure, and comprising respective radiation detectors and angular orientators. A control unit drives the motor assembly to position the support structure in a plurality of positions with respect to the housing, and, while the support structure is positioned in each of the plurality of positions, drives the orientators to orient the respective detectors in a plurality of rotational orientations with respect to the ROI, and to detect radiation from the ROI at the rotational orientations. Other embodiments are also described.